Pneumatic hammer



y De@ 7, 1937. E. w. STEVENS PNEUMATIC HAMMER 4 Sheets-Sheet 1 Filed Sept. 11, 1955 E Vw, M d um. f

INVENTOR Eon/A20 l/V Sra/EMS.

E. w. STEVENS 4 Sheets-Sheet '2 INVENTOR U Nw DCC- 7, 1937. E. w. STEVENS PNEUMATIC HAMMER Filed Sept. ll, 1955 4 Sheets-Sheet 5 www u@ MM. QN

` lNvl-:N-roR H4 STEKENG.

ATTORNEY Eon/Alea Dec, 7, 1937. E W, STEVENS 2,101,159

PNEUMATIC HAMMER INVENTOR Eon/ARD Wn-re-Ns.

ATTO RNEY Patented Dec. 7, 1937 UNlTED ,STATES L,2,101,159 rNEUMA'rrc HAMMER Edward W. Stevens, Detroit, Mich., assigner to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application September 11, 1935, Serial No. 40,038

6 Claims.

'I'he present invention relates to fluid pressure percussive tools Aand more particularly to -single acting riveting hammers adapted to head a rivet in one blow.

An object of theinvention is to enable a pero sive tool to deliver a powerful blow forits size initial movement of the throttle valve and its completely open position. In the operation of prior constructions of this type, the piston starts to move just as soon as the throttle valve begins to open and travels rapidly toward the frontl end of the cylinder before the operator has an opportunity to complete the valve movement. Consequently, full pressure is not delivered to the cylinder until after the piston has drifted a considerable distance away from its starting point.

In accordance with the present invention the piston is actuated by full pressure during lits e`ntire stroke yresulting in increased velocity and force of blow. This result is accomplished by a v novel throttle arrangement which retards movement of the piston away from its normal position until the opening movement of the throttle valve has been completed. y

Another object is to enable the operator to control the force of blow in response to either a quick or slow throttle valve movement.

A further object is the provision of a one-shot riveting hammer which is light in weight, easy to manipulate, and in which the piston is quickly restored to normal position after each forward stroke whereby the machine may deliver blows in rapid succession under the control of the operator.

In accordance with the invention, live `air is normally supplied to the front end of the cylinder to hold thepiston at the opposite end. A manipulative trigger controls an inlet and an exhaust Valve, so constructed and'arranged that movement ofthe trigger rst cuts off the holding pressure in front of the piston, then admits live v air to a cylinder port intermediate the ends of the piston. A feature of the invention resides Ain means for preventing the air admitted through said port from starting the piston forwardly until the trigger has completed its movement. Such means comprises an exhaust port at the extreme rear end of the cylinder which vents the air leaking around the peripheral surface of the piston.

Other objects and features of the invention will appear more clearly from the following de- 5 scription taken in connection with the accompanying drawings and appended claims.

Referring to the drawings, Fig. 1 is a longitudinal'l view, partly in section and partly in elevation of a riveting hammer embodying the invention, 10 showing the position of the parts during the time the piston is driven forwardly;

Fig. 2 is a longitudinal section showing the piston on its rearward stroke; v

Fig. .3 is an elevational view, looking upwardly, 15 of the riveting hammer shown in Fig. l;

Fig. 4 is a longitudinal section showing the ex'- haust valve in normal position and taken through an irregular plane to show passages under control of said valve; l 20 Figs. 5 and 6 are cross sections, as indicated by the arrows 5--5 and 6-6 respectively in Fig. 2;

Fig. 7- is an end view in elevationlobking from y left to right in Fig. 1; l

Fig. 8 is a fragmentary longitudinal section cor- 25' responding to Fig. 4 but showing the exhaust valve in operated position; andy Fig. 9 is a fragmentary longitudinal section looking in the direction of arrows 9-9 in Fig. '1, the valves and operating trigger being shown. in 30 an intermediate position of movement.

The illustrative riveting hammer lcomprises a cylinder I0 providing a piston chamber Illa in whichy reciprocates a hammer piston Il adapted to strike the end of a riveting tool I2 which is 35 mounted in a chuck bushing I3 in the frontend of the cylinder. A collar I4 (see Fig. 4) on the working tool abuts against the bushing on its inner face and is adapted to engage a retainer 40 I5 on its outer face. The tool I2 has a concave outer end I6 which engages thehead of a rivet (not shown).

The tool I2 and bushing I3 serve as a closure fory the front end of the piston chamber while the '45 rear end thereof is closed by a threaded block I8.

f The block retains the cylinder I0 in assembled relationship witha grip handle I9 having a bore 20 and counterbore 20a to fit theoutside surface of the cylinder. The grip handle has an inlet 50 duct 2|,l 2Ia adapted to be connected to a uid lpressure supply line (not shown) and has an exhaust duct 22,1eading to atmosphere. Connections are provided between d ucts 2I and 22 and the respective ends of the piston chamber 55 under control o! an inlet valve 24 and an exhaust valve 25, both mounted in the handle.

-Valve 24,has a stem 24a slidable in-a bore in the grip` handle I9 and has a head 24b engageable with a seat 24e to control communication between supply duct 2|a and a counterbore 21 in the handle. A spring 28 is interposed between the valve head 24h and a plug 29 to hold the valve head yieldingly against its seat. Counterbore 21 is connected by a large port 30 to the cylinder. Port 30 delivers live motive iluid to the cylinder during the forward or working stroke and serves as an exhaust port on thev return stroke. To enable the cylinder to exhaust through port 30 the counterbore 21 at the lower end of this port is adapted to be connected to exhaust passage 22 by means under control of the exhaust valve 25.

Exhaust valve 25 is in the form of a plunger mounted to reciprocate in a sleeve 32' xed'to the handle I 9. Near its rear extremity, the sleeve has a port 32a registering with exhaust passage 22, and a port 32h registering with port 22a leading to the counterbore 21. Plunger 25 is adapted selectively to cover and uncover ports 32a and 32h to control the ow of exhaust air from cylinder port 30 throughvcounterbore 21 and said ports to the exhaust passage-22. Inward movement of the plunger 2'5 isi resisted vby compression spring 33 extending within a recess in the plunger.

, .25 abuts against a trigger 3,4 mounted on a pin The forward or outer end of the exhaust valve and having a stop 34a which limits outward rocking movement of the trigger and consequently forward movement of the plunger 25. The trigger and valve are guided by a tongue 34h on the trigger which fits in a slot 25bin the plunger valve .25.

Normally piston Il is held at the rear ed of the piston chamber by means, under control of exhaust valve 25, for simultaneously exhausting the rear end and supplying pressure iluid to the front end oi the cylinder. Referring to Figs. 4, 5, 8, and 9, the rear end of the cylinder Vis adapted to be exhausted through passage 36p sleeye'port 32c, the interior of sleeve l2 and port 32a to the exhaust passage 22. I'he means for supplying prssureiluid to the front end of the cylinder comprises passage 31 (see Fig. 4), leading from live air duct 2|La to a port 32d which is in the same radial plane as port 32e, both ports being adapted to register with the annular groove 25e when the plunger 25 is in its normal position. Port 32e registers with passage Il communicating with tube/'39 extending toward. the frontend of the cylinder. Near the .front end 0f the piston chamber I0a,'t he cylinder has a boss 45 prqvided with a recess 4| communicating through a` port 42 with the interior of the cylinder. At the outer end of the cylinderport 42 is a seat 43 for a hollow valve 44- guided within recess 4|.v Valve 44 controls communication between cylinder port 42 and radial ports 45 in the boss 40 which lead to atmosphere.l The outerl end of recess 4| is closed by a threaded cap 41. Pressure iiid supplied by tube 39 passes through passage 45, then under cap 41 to the interior of the hollow valve 44 to hold the valve against its seat4 and thereby wut-oi! port 42 from'atmosphere. At the" same time,J a limited supply of pressure Yiiuid passes through a small orifice 44a in the valve and through port 42 to the front end ot the piston chamber lila to return the piston and hold it at the rear end of the piston chamber. Due to the larger diameter of recess 4I as compared with 75 port 42', and the drop in pressure of air passing is cut off from the front end of the piston cham 'ber lila, the exhaust valve 25 closes ports 22a and 32h (see Figs. 2 and 9) from exhaust.

time the throttle valve 24 is only partly open, the

, position indicated by broken lines in said gure.

At this time holding pressure is transmitted from live air duct 21a to grip handle passage 31 (see Fig. 4) 'around exhaust valve groove 25e, through passage 38, tube 39, passage 48, valve on'iice 44a and cylinder port 42 to the front end of the piston chamber I 0a, thereby holding the piston il at the rear end of the cylinder. Holding pressure uid escaping between the piston and cylinder toward the back of the piston I I is intercepted by an annular groove i'i'a in the piston `and is exhausted through ports 30, 22a, 32h, 32a and 22. As seen in Figs. 4, 5 and 9, the extreme rear end of the piston chamber Ia at this time is `@pen to exhaust through passage 36, sleeve ports 32e and 32a and passage 22 which supplement the action of groove I ia and port 30 in preventing the building up of pressure behind the piston at this time.

As the operator pulls thev trigger 34,'he first actuates the exhaust valve 2'5 to move the valve groove 25e (Fig. 4) `out of register with `fluid pressurevsupply port` 32d thereby cutting oi the supply of holding pressure through tube 39 to the front end of the piston chamber lila and releasirig the valve 44 atthe front end of the cylinder.

About the same time that the holding pressure Having discontinued lthe supply of holding pressure iiuid from the front end of the piston chamber Illa and disconnected the counterbore 21 from .exhaust (through port 32h), the device is in condition to admit live pressure iluid to the cylinder for driving the` piston forwardly. Fur- -ther movement of the trigger is transmitted through stem 24a to open the inlet valve 24, which admits live pressure fluid from inlet duct 2In around the valve head 2'4b and through counterbore 21 to cylinder port I0 which registers with piston groove Ila. In this intermediate stage of operation, and before the trigger has been moved to its extreme rearward position in which the throttle valve is wide open, the parts of the device occupy the positions show n in Fig. 9.

It will be noted from Fig. 9 that during the 5 extreme rear end of the piston chamber Ilia is .5

open to exhaust through passage 38, sleeve ports 3 2c and 32a and exhaust passage 22. 'Ihe purpose of keeping these exhaust passages open after the throttle valve has started to unseat, is to prevent premature movement of the piston/diy venting the air that seeps from piston groove Ila overthe circumference of the piston to the rear face of the latter. Movement of the piston is also retarded by the friction between the piston and cylinder, since the unbalanced ,area of the piston exposed to port 3l tends tiiA force the piston against the opposite or upper- Wall of the cylinder.

Movement of the trigger 34 toits final position opens the `throttle valve 24 wide and cuts on the rear end of the cylinder from exhaust at the ports 32e and 32a, which permits pressure to build up behind the piston and shift the piston until it luncovers inlet port 30, which by-that time is supplied with full pressure adapted to actuate the piston during substantially its entire stroke to deliver aheavy blow against the working tool I2. During the forward stroke, air is exhausted from the cylinder through ports I2 and 46, as shown in Fig. l. The valve 44 isheld inthe Fig. l posi tion by the predominance of `pressure on its upper end, inasmuch as the lowe'r end is connected to exhaust through passage 48, tube 39, passage, 38, sleeve port A32 and valve slot 25h (see Figs. 8 and 9).

When the trigger is released, spring 33 restores it to the position shown in Fig. 2 and the piston is automatically returned to the rear end of the cylinder, and held there until the next operation,

, by pressurefluid through passage 31, valve groove was actuated by a quick manual movement, the

valve remained only partly open during a considerable portion of the travel of the piston.

lIt is sometimes desired to deliver a blow of less than maximum force, and this can be accomplished by moving the trigger 34 very slowly,` to allow time for pressure to build up in back of the piston whilev the exhaust ports 32e and 32a are being slowly covered. Pressure behind the piston may then cause it to move before the throttle valve is opened wide. Thus the invention prov ides `for either` a light or heavy blow depending on the trigger action. A fast movement of the trigger provides full line pressure to the rear face of the piston, the instant the port 30 is uncovered andallows full pressure to be exerted on the piston throughout the full forward stroke. A slow operation of the trigger produces a slow start and slow acceleration of the piston, as well as a restricted ow of live air to follow up the piston on its workingstroke. The lightness of blow is governed entirely by the speed with which the trigger valve is ropened.. 'I'he slower it is opened the lighter will be the resultant blow.

While the invention has been particularly udescribed with reference to a single 'illustrative 'embodiment, it will be apparent that many changes and adaptations thereof may be made within the spirit of the inventionl and withinmthe scope of the appended claims. What is claimed is:

l. A percussive uid pressure operated tool lof the single impact type comprising a cylinder providing afpiston chamber, a hammer piston reciprocable therein, manually controlled means lfor admitting pressurev fluid to. the rear end of the piston chamber to drive the piston forwardly, means for admitting holding 'pressure iluid to the front end of the piston chambeato return the piston and -hold it normally at the rear end of the cylinder, and means for intercepting holding pressure fluid seeping toward the rear of the piston, said last-named means comprising an annular groove in the piston and a cylinder port 70 connected to exhaust, said port/'being positioned to register with the groove when the piston is l the cylinder, and means for retarding the buildlng up of pressure behind the piston in response to pressure uid seepage toward-the rear of the piston,` said last-mentioned means comprising an annular groove in the piston and a cylinder port connected to exhaust, said port being positioned to register with the groove when the piston is held at the rear end of the cylinder, and an exhaust passage communicating with the extreme rear end of the piston chamber.

3. A percussive fluid pressure operated tool according to claim 2 in which manually controlled means are provided for rst disconnecting said cylinder port from exhaust, then admitting live pressure fluid to said cylinder port, and then closing said exhaust passage. 4 l

4. A percussive tool comprising a cylinder providing a piston chamber, a piston reciprocable therein, an inlet passage in said cylinder connected at one end to a source of live pressurev fluid and at its other end terminating in a port in said piston chamber near the rear end of the latter, a passageway leading from the .extreme rear end of the piston chamber to exhaust whereby tov oppose the building up of pressure behind the piston, and means for cutting oi said passageway from exhaust during the time that pressure fluid is being supplied to said inlet passage.

5. A fluid pressure operated percussivetool of the single impact type comprising a cylinder providing a piston chamber, a pistonI reciprocable therein, a. source of live pressure fluid, a pair of ports in the cylinder, one of which is at the front end of the piston chamber and the other of which is near the rear end thereof, a grip handle connected to the rear end of the cylinder, a throttle valve in said handle, adapted in oneposition to connect the rear cylinder port to said pressure iiuid source, a second valve in said handle, a passagewayy from said second valve to the front cylinder-port, said second valve being adapted to connect said passageway to live pressure fluid and slmultaneouslyconnect the rear port to exhaust, and a single-manipulative trigger engageable with both valves, said ,trigger being adapted by continuous movement in one direction ilrst to 'actuate the second-mentionedvalve to cut oif the supply of pressure fluid to the front end of the s. A percussive tool according to claim 5 in` i which an exhaust passage is provided for ythe extreme. rear end of the cylinder' and the sec.

ond-mentioned valve is` arranged to close said passage-prior to the time that the throttle valve is moved to completely open positiom to" admit live pressure fluid to said rear cylinder port.

, EDWARD W; STEVENS.

CERTIFICATE OF CORRECTION. V Patent Ne.` 2,101,159'. December 7, 1957.v

EDWARD w. sTEvENsx 'l It 1s hereby' certified that error appears in the printed specfation of the above numbered patent requiring correction as follows: Page 5, secod columr-l, line 59, claiml 54, after "fluid" insertthe words through said passageway; andthe-t the said Letters Patent should be read with this correction therein that the name may conform to the record of the case the Patent officer r `.signed and sealed this 8th dey er February, A. D. 1958.

Henry Veml Arsdale (Seal) a Acting Commiasion'er of Patents.` 

